为了实现大幅度提高内燃机工作热效率的突破，内燃机领域出现了很多种新型循环内燃机。本文从数种一些典型新型循环内燃机具有中总结出两点共性特征：工质移缸和喷水做功两大共性技术特征。研究这两个技术特征，对于揭示内燃机节能原理和开发节能内燃机具有重要意义。在一台常规四缸四冲程汽油机基础上，为了研究新型循环内燃机的节能原理与应用基础，本文作者设计并改造了出一款兼具工质移缸和喷水做功技术特征的试验用复合循环内燃机。该内燃机的一个工作循环由前后两个四冲程气缸完成，前缸为传统的燃烧缸，后缸为喷水缸。前缸的燃烧废气通过转接管送入后缸，后缸通过喷水做功提高工作效率。试验表明，在低负荷工况下，复合循环内燃机可以直接通过工质移缸降低燃油消耗率；在高负荷工况下，复合循环内燃机则可以通过喷水做功降低燃油消耗率。复合循环内燃机工质移缸节能的本质是燃烧废气的二次膨胀。根据膨胀缸的工作模式，二次膨胀可以分为四冲程二次膨胀和二冲程二次膨胀。与传统内燃机相比，四冲程二次膨胀的节油工况集中在低负荷区域，而二冲程二次膨胀的节油工况则集中在高负荷区域。因此，本文提出了2/4可变冲程二次膨胀内燃机概念，该内燃机的膨胀缸可以根据工况切换工作模式，它的高效工况可以覆盖一般车用内燃机的所有常用工况。在喷水做功方面，本文通过对固定容积气缸高温气体中喷水研究了喷水做功的节能机理，发现闪蒸现象可以提升喷水做功的能力。本文总结出了“一低两高”的喷水做功类内燃机设计目标：喷水时缸内压力尽量低、喷水水温尽量高，以及气缸壁面温度尽量高。根据此目标，在复合循环内燃机的基础上，本文提出了缸内闪蒸喷水内燃机概念。该内燃机在缸外利用高温燃气对水预热以提高喷水温度；通过高温燃气对后缸缸壁预热以提高后缸壁面温度；在喷水前将燃气排出后缸以降低喷水时缸内压力。根据仿真研究，该内燃机可以提升内燃机扭矩15.4%，降低油耗9.4%。内燃机气缸内喷水会造成气缸湿壁的现象，导致活塞环与气缸壁摩擦阻力增加和磨损加剧的问题。为增强内燃机气缸壁的疏水性，本文提出了利用椭圆振动纹理加工（EVT）的方法，在气缸壁与活塞环的接触面上加工出结构化纹理。试验结果表明EVT可以通过改变加工参数控制材料表面的疏水性，利用凹坑表面纹理获得较大的材料表面疏水性。

To improve the efficiency of internal combustion (IC) engine, there are many new cycle IC engines. Two common characteristics can be drawn by summarizing some typical new cycle IC engines, which are charge transit and water injection. Studying these two common characteristics has the great significance to explain the IC engine energy-saving principle and develop the high efficiency IC engine.To study the energy-saving principle and application foundation of these new cycle engines, the author developed a test co-cycle engine based on a traditional 4-cylinder 4-stroke gasoline IC engine, which had the technologies of charge transit and water injection at the same time. The working cycle of the co-cycle engine is formed by one former cylinder and one later cylinder. The former cylinder is a traditional 4-stoke combustion cylinder, while the later cylinder is a 4-stroke water injection cylinder. The burned gas of former cylinder is transferred into later cylinder by a connection pipe, and the water is injected into the high temperature burned gas to evaporate and work in the later cylinder. By the experimental study, it was discovered that, compared with the original engine, the co-cycle engine could achieve lower fuel consumption just by charge transit in low load conditions, and the co-cycle engine could save energy by water injection in high load conditions.The energy-saving principle of the co-cycle engine by the charge transit in low load conditions is secondary expansion of the former cylinder’s burned gas. According to the working mode of the expansion cylinder, the secondary expansion engine could be separated into two working modes, which are 2-stroke secondary expansion and 4-stroke secondary expansion. Compared with the traditional engine, the 4-stroke secondary expansion working mode could save energy in low load conditions, while the 2-stroke secondary expansion working mode has higher working efficiency in high load conditions. Therefore, the author proposed a 2/4 stroke switchable secondary expansion engine concept to save energy in both low and high load conditions. According to the simulation study, the energy-saving working condition of this new concept engine could cover all of the frequently-used conditions of a normal vehicle.For the water injection energy-saving technology, the principle is studied by the water injected into high temperature gas in a fixed volume cylinder. It was discovered that the flashing boiling of water injection could improve the evaporation power capability. The author summarized three designing aims of the water injection engine, which are ‘one low and two high’. The cylinder pressure should be low when the water injected into the cylinder, the water temperature should be high before injection, and the cylinder wall temperature should be high. Based on these aims, a flashing boiling water injection IC engine concept was proposed in this paper. Compared with the co-cycle engine, this new concept engine could pre-heat the water by the high temperature burned gas outside the cylinder, pre-heat the cylinder wall by the burned gas after heating the water, and exhaust the burned gas during the second stroke before water injection to decrease the cylinder pressure in the later cylinder. According to the simulation, compared with the traditional IC engine, this new engine could improve the torque by 15.4% and decrease the fuel consumption by 9.4%.The cylinder wall may get wet when the water is injected into the cylinder, which may increase the friction loss and wear. To improve the hydrophobic performance of the cylinder wall, the elliptical vibration texturing (EVT) is proposed in this paper to generate different patterns on the cylinder wall and piston ring surfaces. The experimental study showed that the surface wettability can be controlled using EVT just by carefully choosing the process parameters. The surface hydrophobic performance can be improved by the dimple patterns.